Working The Cluster

Working The Cluster Network.

The Basics.


The Southwest cluster is made up of a number of independent Repeaters operated by their own Repeater Groups working in tandem to create a big, if not the biggest UK network of DMR repeaters to date.

Each Repeater Group owns and operates their repeater and internet feed. Groups can join or leave the Southwest Cluster (SWC) there is no restrictions or demands on them, it is a truly independent network. The only thing we ask of you the user of the SWC is to show you’re thanks to the operators of your local repeater by joining their group and maybe make a donation to help with the running costs. Remember repeaters are not sponsored by Ofcom or the RSGB, they are totally paid for by the repeater group.

The Repeaters.


Each repeater provides the following characteristics:


  • One single 12.5KHz wide RF Chanel that is divided into two 6.25KHz wide sub channels called Timeslots (TS).
  • Each of the two Time Slots (TS) can carry separate voice QSO’s.
  • The repeater “Controls” your terminal (The technical name for your radio). If your terminal is correctly configured, it will not transmit until the repeater tells it to, even if you are squeezing the life out of the PTT button.
  • Just like the Analogue repeater equivalent, the DMR repeater also transmits beacons at intervals, and just like you, the repeater is required by Ofcom to transmit its callsign periodically. However, unlike you or your standard FM repeater, a DMR repeater sends both a callsign by AFSK (FM Audible) and a digital beacon. The later is processed by your terminal and is used as part of the roaming feature.
  • Each repeater uses two Talkgroups (TG) one per (TS). Although DMR itself can handle hundreds of TGs, (See below for description of TG’s), the SWC network keeps things simple by just using two TG's.
  • TS1/TG9 This Talkgroup remains local to your repeater; it is not relayed to the other SWC member repeaters. However, this TG is special in that it allows a feature called Dial on Demand (DoD).
  • Dial on Demand (DoD) is a special system where you can request the SWC central server to connect your communication to another repeater, or Talkgroup which can be outside of the Southwest, indeed it could even be to a TG outside the UK (see below details about FreeDMR).
  • TS2/TG950 will cause your local repeater to relay your audio to all other SWC member repeaters across the Southwest.
  • D-APRS & GPS tracking is currently NOT supported, so please ensure this is turned OFF in your Rigs Code Plug.


Dial on Demand (DoD).


This feature is enabled on a repeater by repeater basis and can be disabled on request of the repeaters keeper.


Unlike the MK1 SWC network which was limited to TS2/TG950 being SWC wide and TS1/TG9 being local only. The introduction of our own FreeDMR server now takes us beyond this limitation. We can now offer Dial on Demand (DoD)Talkgroups.
This is ONLY available to DoD enabled repeaters and then ALWAYS on TS1/TG9.


DoD does **NOT** require you to program hundreds of channels with different Talkgroups and Timeslots. DoD makes programming the radio terminal simple. Your terminal only requires TS1/TG9 and TS2/TG950 !!

Two channels per repeater, that’s it, simple!


**Before** you use TS1/TG9 or the DoD function it is imperative YOU LISTEN to the Timeslot. This will ensure that no-one has left the TS dialled into a DoD already, or there is not a QSO already in progress.


So to use DoD change your radio channel to TS1/TG9 on your local repeater, decide what DoD Talkgroup you want to  connect to for example 2350 (UK Wide) . At this point your ready to make a DoD connection.
You will need to know how to get to the “Private call” option on your radio menu. Because of the wide number of terminal manufactures, it is advisable for you to read your operators manual.  

Once the private call function is selected,  simply enter the number of the TG you want to connect to and then simply press and hold the PTT for 2 seconds, then release.

If your DoD connection is sucessful you will hear the TG number read back to you.

When you have finished your QSO repeat the above steps to get to the “Private call” menu, but this time enter the magic code of 4000 then transmit for 2 seconds and release. The system will report “Not connected” this means you have returned the repeater to the local TG9 only..

Good operator practices improves the quality of QSO's taking place on the DMR mode. It is recommendeed you leave a good gap between overs.  This allows people to disconnect from DoD sessions and others to break into your QSO if needed.

  • If you link to a DoD Talkgroup and do not transmit and just monitor, the system will automatically disconnect the DoD TG after 10 minutes of voice inactivity.
  • Then after 15 minutes of inactivity the repeater will resume sending spoken beacon annoucments confirming the repeater you are listening to.


Please 'click' to enlarge the instruction sheet below. We recomend this is then printed and used in cojunction with your terminals (RIGS) manual as a handy guide to Dial on Demand (DoD).

Below is a list of all the Repeaters linked into the South West Cluster Network.

Repeater Channel List